Torque Density Optimization of Six-phase Permanent Magnet Synchronous Machine

Compared with the three-phase permanent magnet synchronous motor (PMSM), the six-phase PMSM has better winding fault-tolerance performance, which greatly improves the safety of the electromechanical actuation (EMA) of the aerospace crafts. The typical structure of the six-phase PMSM is 12 slots, 10 poles, concentrated winding, parallel magnetization, and has the ability to restrain short-circuit current. Although parallel magnetization is simple, the output torque is limited. In this paper, a magnet array design method based on parallel magnetization, oblique magnetization, and tangential magnetization is proposed, which improves the torque density of the six-phase PMSM and reduces the torque ripple at the same time. According to the specific requirements of the EMA, four six-phase permanent magnet synchronous motors with different magnet arrays including parallel magnetization are designed. Through finite element analysis (FEA), the air gap radial magnetic density of different magnet arrays is obtained. The influence of the air gap radial magnetic density on the output torque and torque ripple is analyzed. The simulation result shows that the proposed magnet array design method can improve the torque density of the six-phase PMSM and reduce the torque ripple compared with parallel magnetization.